Showing papers on "Forward converter published in 2019"

Implementation of Bidirectional Resonant DC Transformer in Hybrid AC/DC Micro-Grid

Abstract: As a reliable device for voltage regulation and isolation, a line frequency transformer is commonly connected in series with bidirectional converter (BIC) to interlink the ac and dc networks of hybrid ac/dc microgrid. However, it may not be suitable for the applications where weight and space occupation are of important concerns such as hybrid ac/dc microgrid. In this paper, bidirectional resonant dc transformer (BRDT) is proposed to replace the conventional bulky transformer for bus voltage matching and galvanic isolation. In order to simplify systematic coordination with BIC and central controller, BRDT is designed as an ideal transformer with simple open-loop scheme. 50% duty ratio scheme is implemented as it has been proven to be better than the phase-shift scheme in order to ensure BRDT conversion efficiency. A generalized model for various BRDT topologies, including CLLC, CLL, and LLC high frequency transformer (HFT), is established for analysis. The impacts induced by the transformer leakage, magnetizing inductances, and extra resonant capacitors are considered when designing the HFT. The conversion gain of the designed BRDT has also been analyzed in the full power range. Lab-scale prototypes for BRDT and hybrid ac/dc microgrid have been developed for experimental verifications. The performances of BRDT and system in both steady and transient states have been confirmed.

A Unitized Multiwinding Transformer-Based Equalization Method for Series-Connected Battery Strings

Abstract: Active equalization is an efficient method to improve the performance of series-connected battery strings for the electric vehicles. However, the large-scale applications of the active equalization are restricted by many factors, such as system cost, control complexity, and equalization speed. In this paper, a unitized multiwinding transformer-based equalization method is proposed. The forward converter and flyback converter are realized, simultaneously. The forward converter principle is used to equalize the battery cells in the same subunit, while the flyback converter principle is applied for the equalization of the different subunits. Fewer metal-oxide-semiconductor field-effect transistors and transformer windings are needed for lower control complexity and lower system cost. Furthermore, different subunits of the battery string can be simultaneously equalized, resulting in higher time efficiency. To verify the proposed method, the simulation and experimental workbenches are established. Results indicate that the proposed method can equalize well both for the cells in different subunits and in the same subunit. The urban dynamometer driving schedule tests are further applied and the unbalanced problem is covered in about one hour. The results show that the proposed method has achieved a good performance of equalization in terms of system cost, control complexity, and speed.

Novel Integrated Three-Port Bidirectional DC/DC Converter for Energy Storage System

Abstract: The study proposes a novel integrated three-port bidirectional dc/dc converter for energy storage systems. The converter includes two batteries, namely 24- and 48-V batteries, used as input source and for backup energy, respectively. Each battery can supply to dc load in the normal case. When the grid power fails, 24-V battery input is stepped up to the dc bus through a high step-up converter. The 48-V battery serves as a buffer power supply when the load increases instantaneously. At night, when the 48-V battery is under low power consumption, the dc bus can charge the battery. In addition, the converter can monitor both battery voltages simultaneously; when one battery is used excessively, the other battery can charge it, thus keeping the system power stable. The integrated three-port bidirectional dc/dc converter is a combination of a boost-flyback, forward converter, and voltage doubler and has the following advantages: 1) it operates in input continuous current and low voltage stress; 2) it provides input current recovery; 3) it improves high reverse voltage caused by the transformer; 4) it operates in zero current switching (ZCS); and 5) its doubler circuit can flexibly adjust the dc bus voltage. A 500-W three-port bidirectional dc/dc device was implemented to verify the feasibility and practicability of the proposed converter. The highest efficiency achieved for operation in 24-V battery high step-up mode was 95.3%; it was 94.9% and 95.2% in 48-V battery step-up and step-down mode, respectively.

Multi-Winding Configuration Optimization of Multi-Output Planar Transformers in GaN Active Forward Converters for Satellite Applications

Abstract: It is a serious challenge to find the optimal winding configuration that realizes minimum leakage inductance of multi-output multi-winding planar transformers due to the complex coupling relationship. The proposed idea is to build the mathematical model of leakage magnetic field energy and screen out all possible winding configurations to solve the minimum value with MATLAB programming. Then, only limited potential winding configurations need to be three-dimensionally simulated in Maxwell. By analyzing the inductance matrix, the leakage inductance of multi-winding planar transformers is solved. A full gallium nitride (GaN) active clamp forward converter with self-driven synchronous rectifiers (SRs) is presented with complete mode analysis. It is noted that the proposed active clamp technology uses the auxiliary winding with the nonfloating GaN switch compared to the conventional high-side clamping circuit, which is important for the satellite applications. The GaN drive chips for high reliable gate voltage are combined with self-driving. Considering the leakage inductance in each winding and junction capacitance of the GaN high electron mobility transistors, the oscillation frequency and amplitude over the switches are modeled quantitatively, which is important to minimize powertrain loop at MHz. The explanation of the root cause of the voltage spike in the converter is also presented. A prototype with 1 MHz, 100 V input, 5 V/6 A and ±12 V/0.83 A outputs was built to verify the proposed techniques.

Active-Clamp Forward Converter With Lossless-Snubber on Secondary-Side

Abstract: This paper proposes a novel active-clamp forward converter (ACFC) with a lossless-snubber on the secondary-side, which combines a resonant capacitor and a clamping diode with an output inductor in parallel. The conventional ACFC achieves zero-voltage-switching on switches of the primary-side during dead time for reducing the switching loss and voltage spike. Unfortunately, on the secondary-side of transformer, the voltage spike damages the free-wheeling diode and rectifier diode due to the reverse recovery current and junction-capacitor of the diode and leakage inductance of the transformer. This paper proposes a lossless-snubber on the secondary-side operation for reducing the voltage spike on the free-wheeling diode and forward-rectifier diode. Therefore, the converter proposed in this paper is suitable for high-output-current applications. Experimental results are shown to verify the analysis and design procedure of the proposed forward converter.

Forward converter current fed equalizer for lithium based batteries in ultralight electrical vehicles

Abstract: In this paper, the concept of a forward balancing technique fed by a buck converter for lithium-based batteries in Electrical Vehicle (EV) applications is investigated. The proposed active topology equalizes eight cells in a series in a battery pack, by using a forward converter for each battery pack and the whole battery packs, using a buck converter. The battery bank consists of four battery packs, which are in series. Therefore, the proposed system will equalize 32 cells in series. In this paper, the proposed circuit employs a single transistor used in a Zero Voltage Switch (ZVS) for the forward converter. In practice, this means a capacitor in parallel with the switch at the same time a demagnetizing of the transformer is obtained. The circuit realizes a low Electromagnetic Interference (EMI) and reduces ringing. To overcome the problem of many pins on a coil former, the transformer secondary windings are made by using hairpin winding, on a ring core. It permits, e.g., having eight secondaries and uniform output voltages. Each secondary winding is made by two hairpin turns using two zero-Ohm resistors in series. The proposed topology has less components and circuitry, and it can equalize multiple battery packs by using a single buck converter and several forward converters for each battery pack. Experimental and simulation results are performed to verify the viability of the proposed topology.

Design, modelling, and implementation of a modified double-switch flyback-forward converter for low power applications

Abstract: This study proposes a modified double-switch flyback-forward (DSFF) converter for low-power applications with a reduced number of windings in its transformer. This circuit has resulted from the combination of the two-switch flyback and two-switch forward converters. It includes a simple transformer with one set of secondary side windings, and it is not necessary to design two separate sets of windings for the desired output voltage which is the main problem of other flyback-forward converters. An auxiliary winding has been designed for self-biasing, and consequently, it improves the overall efficiency in the no-load condition. Due to the modifications on the previously presented two-switch flyback-forward converter, the circuit model has changed. This study, first, analyses the operation of the proposed converter in detail, then it explains a method to design this converter in continuous inductor current mode. Also, a start-up voltage regulator circuit and a modified bootstrap gate driver will be investigated, and the DC and AC model of the converter will be presented. Experimental results validate the proposed DSFF converter. The tested circuit includes a DSFF converter, a pulse generator circuit, a start-up voltage regulator, and a modified bootstrap gate driver.

A Three-Phase Single-Stage Isolated Flyback-Based PFC Converter With Leakage Energy Recovery Clamping Circuit

Abstract: This article presents a three-phase single-stage isolated flyback-based power factor correction (PFC) converter with a clamping circuit to recover the transformer leakage inductance energy for more electric aircraft application. With the proposed clamping circuit, the transformers’ leakage inductance energy is successfully captured in clamping capacitor, and subsequently, a constant power 28-V secondary supply is derived by using a two-switch forward converter to improve the converter overall efficiency. The converter unity power factor (UPF) operation is obtained by using the inherent resistance property of discontinuous conduction mode (DCM). Hence, the input current shaping circuit is eliminated and resulted in a single-loop control system. Thus, the converter control circuit requires only one sensor, which decreases the system cost and increases the system reliability and robustness. In addition, the converter provides fault-tolerant operation for single-phase loss. The converter is analyzed and the design equations are explained in detail. The voltage and current stress equations for all power components are derived and validated with the simulation. The novelty and the operation of the converter are demonstrated with the experimental results from a 2-kW laboratory prototype.

Improved Three Switch-Active Clamp Forward Converter With Low Switching and Conduction Losses

Abstract: The improved three switch-active clamp forward (3S-ACF) converter is proposed in this paper. The proposed converter has minimized the switching loss on all switches of the conventional 3S-ACF converter by simply changing the gate control method without any additional components. Moreover, the modified gate control enables peak and average currents on the clamp diode to be reduced. Though, all switches of the proposed converter have low-voltage stress similarly to those of the conventional 3S-ACF converter. Consequently, the proposed converter can achieve a high efficiency without any additional components. To confirm the operation, features, and validity of the proposed converter, a 180–288 V dc input and 12 V/550 W output laboratory prototype is built and tested.

An LLC-Type Resonant Forward Converter With Adjustable Turning-Off Time Control

Abstract: This paper proposes a LLC type resonant forward converter using adjustable turning-off time control for low power and voltage applications. The new circuit is derived from the conventional LLC converter, and it has simple structure while maintaining decent soft-switching characteristics. The switching losses are reduced by ZVS (zero voltage switching) and ZCS (zero current switching). Also, regulation of the output voltage does not require a small ratio between magnetizing inductor and resonant inductor, so the leakage inductor of transformer can be utilized instead of an external inductor to realize resonance, which makes it possible to use only one magnetic component in the resonant topology. Besides, the adjustable turning-off time control strategy is adopted in the scheme, which optimizes the switching condition while ensuring the wide range operation. In comparison to the traditional PWM (pulse width modulation) control, the proposed control strategy can further reduce the switching loss and improve power efficiency. This is also suitable for the utilization of GaN (gallium nitride) devices due to the requirement of higher switching frequencies at wide input applications. In addition to the detailed theoretical analysis, the validity of the proposed concept is confirmed by the experimental results of a prototype.

A Single Transformer for Active Cell Equalization Method of Lithium-Ion Batteries with Two Times Fewer Secondaries than Cells

Abstract: In this paper, the concept of active cell-balancing technique, by using a multiple-outputs double-forward converter for lithium-ion (Li-ion) batteries, is investigated. It controls two times more cells than secondaries, and it equalizes eight cells in a series. In this method, four secondaries can reasonably be wound with the same back electromotive force (EMF). This means a low pin count on the transformer and a low bill of materials (BOM). The bridge uses four N-channel MOSFETs as switches, which means two times fewer transistors than cells, resulting in fewer switching losses. This scheme is applied for controlling the minimum voltage among the cells of the lithium-ion battery. It uses a multi-winding transformer based on a forward double converter structure. Conventional schemes using a multi-winding transformer for electric vehicles (EVs) require an equal number of secondaries per cell. This scheme requires one secondary for two adjacent cells, thus the number of secondaries is reduced by a factor of two. Also, the redistribution of charge from a high cell to a low cell does not require many switching components and little intelligence to determine low cell voltage detection. The basic principle of this method is to use the overall battery pack voltage as a reference to supply individual cells, using a forward converter containing a transformer with a well-chosen winding ratio. The experimental and simulation results are performed to verify the feasibility of the proposed system.

Analytical Modeling and Design of an Active Clamp Forward Converter Applied as a Single-Stage On-Board DC-DC Converter for EVs

Abstract: In an electric vehicle (EV), two major voltage levels have to be coupled by an on-board DC-DC-converter - the high voltage traction battery of about 400 V and the auxiliary battery of 12 V. Due to the varying state of charge (SOC) of the batteries, the converter has to cover very wide input and output voltage ranges. Considering recent developments in semiconductors, the active clamp forward converter is an interesting topology since only a very small energy is required in the series inductance for soft turn-on of the main switch. In the design process, however, common methods are not suitable because the clamp capacitor voltage cannot be calculated accurately. This paper presents a novel analytical model, which can be used for accurate calculation of the shape parameters. Results show a maximum deviation of 1.8 % from detailed numerical simulations, which proves that the proposed model is an excellent basis for the converter design procedure. A component stress analysis built on this model demonstrates the potential of this topology for the described application.

Analytical Topology Comparison for a Single Stage On-Board EV-Battery Converter

Abstract: DC-DC converters connecting the traction battery with the conventional auxiliary battery in EVs are characterized by a major challenge: The required voltage ratio (gain range) depends on the input and output voltages, both varying considerably with the state of charge (SOC) of their batteries. However, the properties of new wide-bandgap semiconductors lead to modified design requirements of the converter, offering some additional design freedom. This paper presents an analytical converter comparison based on a modified component stress factor analysis. Five converters are compared: The phase-shifted full bridge (PSFB), the LLC resonant converter (half bridge and full bridge with varying operating modes), and the active clamp forward converter (ACFC) (non-interleaved and interleaved). The comparison shows that the ACFC and the LLC with varying operating modes are attractive topologies while the half-bridge LLC converter and the PSFB have generally higher stress values.

Interleaved Active Clamp Forward Converter With Extended Operating Duty Ratio by Adopting Additional Series-Connected Secondary Windings for Wide Input and High Current Output Applications

Abstract: This paper presents a new interleaved active clamp forward converter for low and wide input, and high current output applications. In the proposed converter, the operating duty ratio can be extended over 0.5 due to the additional powering path resulting from additional series-connected secondary windings from each transformer. As a result, the proposed converter can be designed with large transformer turns ratio. Thus, since the proposed converter can reduce not only the primary RMS current but also switch turn- off current, it can achieve high efficiency. Moreover, since all secondary switches can operate without floating gate drivers, the proposed converter can maintain simple structure and low complexity of gate driving circuits in the secondary side. The validity of this proposed converter is verified by the experimental results from 36V–72 V input and 12 V/500 W output for the dc/dc prototype.

A 48 V Input 0.75 V Output DC-DC Converter Power Block for HPC Systems and Datacenters (invited paper)

Abstract: The IBM Power Block is a high power density, low cost 48 V input DC-DC converter, designed to source up to 107 A of continuous output current to processors in high performance computing (HPC) and datacenter servers. Peak efficiency for a 0.75 V output is 90.6% at 45 A and 85.1% at 107 A. An active clamp forward converter (ACFC) architecture uses a pair of primary FETs and a pair of secondary FETs, separated by a planar transformer. A custom timing chip provides four gate timing signals, whose delays can be stored in internal fuses or set through a serial interface. Transformer and inductor magnetics are integrated into a single ferrite structure that allows induced electro motive forces (EMFs) to cancel, thereby providing near zero output current ripple at 0.75 V and low ripple 0.5 V to 1.0 V. Designed for 1 U servers, the Power Block has a 13 mm x 16 mm footprint and a 19 mm height. The electrical output contact’s flat top permits mounting a heat sink or cold plate.

Control scheme design for isolated Swiss-rectifier based on phase-shifted full-bridge topology

Abstract: Swiss-rectifier is a family of high efficient AC-DC topologies. It's a combination of an input voltage selector and two symmetric DC-DC converters. In order to obtain an isolated single-stage rectifier system, the forward converter is used to replace the DC-DC converter in the recently study. However, the hard switching operation of forward converter is unfavorable to increase the working frequency of the magnetic elements. By replacing the forward converter with the phase-shifted full-bridge, the intensive stress of switches is released and the ZVS condition of high-frequency switches can be achieved. Compared with the currently Swiss-forward rectifier, the soft switching modulation mode and duty cycle loss must be considered into the new control scheme of the Swiss phase-shift full-bridge rectifier (SPFR). As a result, the control scheme design is shown in this paper and its characteristics are verified by the experimental results of a prototype.

Analysis and Design of Three Phase Single Stage Isolated Flyback Based PFC Converter with a Novel Clamping Circuit

Abstract: In this paper, a three phase isolated flyback based single stage power factor corrected (PFC) converter with a novel clamping circuit for aircraft application is presented. The steady state operation and design calculations of the converter are presented in detail. The converter is operated in discontinuous conduction mode (DCM) due to its inherent advantages such as PFC, reduced number of sensors, zero diode reverse recovery losses and zero current switching on. The converter requires only one sensor, which makes the system cost effective, more reliable and robust. By using the proposed clamping circuit, the transformers leakage inductance energy is captured successfully in a clamping capacitor, and subsequently a secondary 24V DC supply is derived by connecting a forward converter across the clamping capacitor. The performance of the converter is validated through the simulation and experimental results.

Dual-switch forward converter with an additional reset capacitor for hold-up operation

Abstract: An improved scheme of a dual-switch forward converter is proposed in this paper. Compared with the original converter, the new one can provide higher resetting voltage during the hold-up time interval under the action of an additional reset capacitor. Namely, it allows the converter's duty cycle to be larger than 50%. As a result, the proposed method can transfer more energy stored in the bulk capacitor to the load side during the hold-up interval. Therefore, a smaller bulk capacitor can be used for the converter's hold-up time requirement. Since the additional reset capacitor acts only as a compensation, it would not affect other performance of the converter. The additional circuit can be applied for the dual-switch forward converter when small-volume and high power density are required. The working principle and the performance of the converter are analysed, and the relevant theory formulas are deduced. Then the parameters of key components are given. Finally, the theoretical analysis is validated through a 200 W experimental prototype.

Dynamic Modelling of the Bidirectional Active Clamp Forward Converter with Peak Current Mode Control for Active Cell Balancing

Abstract: This paper presents the dynamic modelling of a bidirectional active clamp forward converter with synchronous rectifier (ACFC-SR) active cell balancing (ACB) applications. A switching model, an average model, and a small-signal model of the converter with peak current mode control (PCM) are developed. The developed models can be combined with the common ACB control system model such that the overall ACB control system performance can be accessed, such as the stability, the robustness against input voltage disturbances, and the tuning of multi-loop control parameters etc. The model-based design of the control algorithm for the overall ACB control system including both battery cell and power converter can be underpinned by the developed model. The influences of the harmonics and fast dynamics due to the use of power electronics on battery cell performance (e.g. battery ageing) will be further investigated. The transfer functions and bode plots of the converter is presented and the simulation results are carried out to verify the accuracy of models.

Input Regulated Soft Switched Ripple Free Current LED Driver

Abstract: This paper furnish an input voltage controlled full-bridge inverter based LED driver. A Double-ended forward converter(DEFC) is used along with full-bridge inverter to regulate the input of full bridge inverter for variations in the supply voltage. Input voltage to the full bridge inverter is sum of primary DC voltage and output of DEFC. Input to DEFC is from primary source. Supply obtained for the proposed configuration can be from DC micro grid. Thus the full bridge inverter is operated with fixed frequency and fixed duty ratio to achieve ZVS over wide range of input voltage variations. Full bridge converter with interleaved operation of output inductor currents is used to achieve ripple free constant current for LED string. In this configuration, power processed by DEFC is low which doesn't influence significantly, the overall efficiency is expected to be high. The proposed circuit configuration analyzed and simulation results are presented.

Interleaved Active Clamp Forward Converters as Single Stage On-Board DC-DC Converters for EVs - an Accurate Model and Design Considerations

Abstract: Wide-bandgap semiconductors qualify the active clamp forward converter (ACFC) as an attractive solution for electric vehicle (EV) on-board DC-DC converters. Recent publications have presented an analytical steady state model allowing the accurately calculation of the clamp capacitor voltage. This is a key design requirement as the voltage is highly dependent on the output current and represents together with the input voltage, the blocking voltage of the primary switches. For higher output powers, two ACFC rails can be operated interleaved on a common output inductor, significantly reducing the size of this coil. In this paper, the model of the ACFC is adapted to its interleaved version resulting in a maximum error of only 2.2 % compared to a switched-model simulation. A component stress analysis based on the model demonstrates the potential of interleaved ACFC in the application of high-power EV onboard DC-DC-converters.

Design and Implementation of 30-W DC-DC Converter with High Reliability and Temperature Characteristics for Military Applications

Abstract: This paper designs and implements 30W DC-DC converters with high reliability and temperature characteristics for military applications, considering US military standards (MIL-STD). Analyzes the performance and specifications of conventional military application products and details MIL-STD items. The proposed converter is designed for guided weapons and aircraft, and it is designed with active clamp forward converter (ACFC) topology for high efficiency. To achieve high reliability, environmental impact test, device selection with excellent temperature characteristics and temperature distribution analysis are performed. The validity of the proposed ACFC for the MIL-STD specification is verified through simulation and experiments. In addition, for comparison with conventional military products, the final designed ACFC performs a performance comparison test with the IR Corporation's ATR2805S product.

Design of a Two-Switch Forward Converter with Master-Slave Active Current Sharing Controller using a Digital Signal Processor

Abstract: Switch mode power supplies (SMPS) such as two-switch forward converters are widely used direct current to direct current (DC to DC) post-converters because of its many advantages and its reliable operation. In this paper, the two-switch forward converter topology was used as basis for the current sharing technique while being controlled by a digital signal processor (DSP). A single DSP will be used in controlling the plant and the current sharing technique. This is to allow the use of lesser component count as well as verify the performance of the DSP when in controlling SMPS running with current sharing. The prototype converter is a 350W converter with input ranging from 320V to 390V with 12V output. Active current sharing technique was used when connecting the supplies in parallel. Current sharing of the converter is limited to converters with the same specifications and topology.

Performance Comparison between a two-switch and RCD clamp forward converters

Abstract: This paper presents performance comparison between a two-switch and RCD clamp forward converters. The performance comparison is carried out through experimentation on the two prototype circuits, which have the same circuit specifications and similar component values. Aspects to be compared include voltage stress of switching components, output voltage regulation, transient response due to a step-load, and efficiency. Test results show that, while the two converters exhibit equal performance on output voltage regulation, the two-switch forward converter has a lower voltage stress on power switching devices, faster transient response, and higher efficiency than the RCD clamp forward converter.

Performance Analysis of Modular Forward Converter in Input Parallel Output Series (IPOS) Architecture Using PI and Fuzzy Logic Controller

Abstract: This paper investigates the performance of modular dc–dc forward converter in Input Parallel Output Series (IPOS) configuration which is controlled by an effective controller. This IPOS topology facilitates the converter to have high output voltage gain. The role of controller is crucial in ensuring the power sharing between the converters. Fuzzy controller, known for its versatility, is employed in this research work. The fuzzy controller feeds appropriate pulse width modulated control signals for appropriate input and load regulation. The performance of the fuzzy controller is analyzed by comparing it with proportional integral controller and a advanced neural network controller. The proposed IPOS system has been analyzed using MATLAB/Simulink environment and hardware prototype. The simulation and hardware results reveal that the suggested topology with fuzzy controller is very effective compared to its counterparts.

Torque Ripple Reduction in High Power BLDC Motors Utilizing an Auxiliary DC to DC Converter

Abstract: Brushless dc (BLDC) motors so far have generally been used for low power servo applications like printers, turntables, robotics etc. Of late they are seriously being considered for application as traction motors in low and medium power electric vehicles(EV) as they possess high torque to weight ratio, and have better operating efficiency. However, they suffer from high torque ripple which makes them unfavourable for such applications. In order to overcome the aforesaid limitation of high torque ripple, several techniques have been reported in the literature. However, the solutions reported in the literature are applicable for low power motors, and not suitable for high power BLDC motors. In this paper a simplified method to reduce the torque ripple of a high power BLDC motor drive utilizing a modified forward converter is proposed. The proposed scheme is able to operate the high power motor with a considerably reduced torque ripple. The efficacy of the proposed scheme is confirmed by performing detailed simulation studies.

Design and Implementation Of a Separate Control Driven High Current Synchronous Rectified Forward Converter with Non-Dissipative Snubber Reset

Abstract: This paper explains the techniques employed in forward converter to maximize the efficiency for a high current output. Usually with high current (>10A), forward converter will have significant diode conduction losses occurring at the secondary side, to minimize it Synchronous Rectification (SR) technique has been adapted with each diode replaced with two SR MOSFETS connected. Lossless snubber is connected across primary MOSFET for resetting of flux in Toff period there by achieving wide range of duty cycle operations. Also, it reduces the voltage stress imposed on the MOSFET and provides zero turnoff switching. Operations and design considerations of the employed techniques are studied. A forward converter has been designed to operate at switching frequency of 100 KHz for 5V/30A output with wide input voltage range of 16V to 45V. The hardware is developed for the proposed design and tested for performance parameters. The results obtained are well within the specified values.

Battery active equalization device with flyback converter

Abstract: The utility model provides a battery active equalization device containing a forward converter, which comprises a driving unit and equalization units, an input anode of the driving unit is connected with a battery anode B +, an input cathode of the driving unit is connected with a battery cathode B-, and an output anode and an output cathode of the driving unit are connected with input ends of allthe equalization units in series to form a loop; the equalization unit comprises an equalization output positive electrode and an equalization output negative electrode which are respectively connected with the positive electrode and the negative electrode of the battery monomer to be equalized; the drive unit and the equalization unit form a series forward circuit driven by an asymmetric half-bridge circuit. The structure of the equalization unit is that a primary side can be subjected to bypass forward conversion, and a secondary side can be subjected to bypass forward conversion. The device can carry out equalization control on any plurality of single batteries at the same time, the equalization efficiency is high, and only controllable switches with the same number as the single batteries are needed except a driving unit without a high-speed power switching device; in the equalization control process, energy supplement can be carried out on the single batteries with relatively lowcapacities, so that the purpose of fully charging the batteries is achieved.

Dispatched Power and Unbalanced Operation of a Three-Phase NPC Based Double-Stage Grid Connected PV System

Abstract: Due to the advancements of technologies, photovoltaic (PV) energy is one of the most attractive alternative energy source in the recent times. Therefore, in this paper a double-stage PV with an isolated DC/DC forward converter and neutral point clamped (NPC) inverter based grid connected 80kW PV system is presented. The dispatched power operation (curtailment of the PV power) is carried out so that the system effectively follows the reference trajectory. Additionally, performance of the system under unbalance grid voltage condition is demonstrated but the control of the unbalanced condition is not considered in this paper. MATLAB/Simulink software is used to verify the system through extensive simulation results.

Active clamp forward converter

Abstract: The present invention relates to an active clamp forward converter. According to the present invention, an apparatus includes: an input power source; a transformer unit including a primary winding and a secondary winding to transform a power inputted from the input power source to output the transformed power; a main switching unit having one end connected to the primary winding and having an opposite end connected to the input power source; an auxiliary winding having one end connected to a contact point between the primary winding and the main switching unit and having an opposite end connected to the opposite end of the main switching unit through a first capacitor; a third switch having one end connected to a contact point among the primary winding, the auxiliary winding, and the main switching unit, and having an opposite end connected to the opposite end of the auxiliary winding through a second capacitor; and a rectifying unit for rectifying the power outputted from the transformer unit to output the rectified power. According to the present invention, in the active clamp forward converter, high power density is achieved through high-speed switching, a switch voltage stress is reduced to reduce a switching loss, and a ripple of a discontinuous input current which causes an electromagnetic interference (EMI) is reduced.